Abstract-We discuss numerical modeling attacks on several proposed Strong Physical Unclonable Functions (PUFs). Given a set of challenge-response pairs (CRPs) of a Strong PUF, the goal of our attacks is to construct a computer algorithm which behaves indistinguishably from the original PUF on almost all CRPs. If successful, this algorithm can subsequently impersonate the Strong PUF, and can be cloned and distributed arbitrarily. It breaks the security of any applications that rest on the Strong PUF's unpredictability and physical unclonability. Our method is less relevant for other PUF types such as Weak PUFs; see Section I-B for a detailed discussion of this topic.The Strong PUFs that we could attack successfully include standard Arbiter PUFs of essentially arbitrary sizes, and XOR Arbiter PUFs, Lightweight Secure PUFs, and Feed-Forward Arbiter PUFs up to certain sizes and complexities. We also investigate the hardness of certain Ring Oscillator PUF architectures in typical Strong PUF applications. Our attacks are based upon various machine learning techniques, including a specially tailored variant of Logistic Regression and Evolution Strategies.Our results are mostly obtained on CRPs from numerical simulations that use established digital models of the respective PUFs. For a subset of the considered PUFs -namely standard Arbiter PUFs and XOR Arbiter PUFs -we also lead proofs of concept on silicon data from both FPGAs and ASICs. Over four million silicon CRPs are used in this process. The performance on silicon CRPs is very close to simulated CRPs, confirming a conjecture from earlier versions of this work. Our findings lead to new design requirements for secure electrical Strong PUFs, and will be useful to PUF designers and attackers alike.
Due to their attractive, regular structure and their simple implementation, crossbar arrays have become one major emerging research area in the fields of nano-devices and electronic circuits. This paper discusses novel applications of crossbars as various types of so-called physical unclonable functions (PUFs) in the field of physical cryptography. The latter is a recent branch of cryptography and security that exploits the inherent, small-scale randomness and disorder in physical structures. PUFs are the currently dominant primitive within this new field. In order to establish the applicability of crossbar structures as PUFs, two crossbars with rectifying junctions are investigated on the basis of real measurement data. In addition, the scalability of these crossbars with respect to their power dissipation and noise margin is evaluated in simulations. The types of PUFs as which crossbars can serve include weak PUFs and super high information content PUFs. We also discu ss whether crossbar-based PUFs allow the erasure and/or rewriting of response information on a single challenge-response-pair level, i.e. without affecting other PUF responses
We have investigated the electronic transport through 3 μm long, 45 nm diameter InAs nanowires comprising a 5 nm long InP segment as electronic barrier. After assembly of 12 nm long oligo(phenylene vinylene) derivative molecules onto these InAs/InP nanowires, we observed a pronounced, nonlinear I-V characteristic with significantly increased currents of up to 1 μA at 1 V bias, for a back-gate voltage of 3 V. As supported by our model calculations based on a nonequilibrium Green Function approach, we attribute this effect to charge transport through those surface-bound molecules, which electrically bridge both InAs regions across the embedded InP barrier.
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